Rechargeable battery packs for insertion in various tools are well known in the art. Generally speaking, these devices usually require two or more batteries electrically connected in series arrangement and encased in some type of housing with an exposed positive and negative terminal for making contact with corresponding terminals in the power tool in which the battery pack is inserted. In general, these battery cells are constructed such that the outer casing is actually the negative terminal of the battery. When a plurality of such batteries are arranged one on top of the other and electrically coupled to each other, the positive terminal is the terminal on the uppermost battery and the negative terminal is the casing of the lowermost battery. The casing of any battery is at a potential equal to the sum of the voltages of the batteries under it. In order to have both the positive and negative terminals near the same end of the battery pack, a connection must be made to the casing of the lower battery and be brought to the top of the pack near the positive terminal. In the prior art, this is done with use of shielded wires which protect the wire and prevent it from making electrical contact with the casings of the uppermost batteries. In another prior art embodiment, the casings are wrapped with an insulating material and a connector is brought from the bottom of the lower casing alongside the battery cells to the top of the battery pack. Further, a fuse element is normally provided for such batteries in the circuit between the positive and negative terminals. In one instance it is in the insulated wire going from the casing of the lower battery to the top of the battery pack. Thus a bulky casing is required to accommodate the size of the fuse in the insulated wire. Further, if multiple voltages are to be provided by the battery pack, an extra terminal is provided at the top of the pack and is connected in some means to a casing of one of the batteries to provide a different voltage than that available at the positive terminal with respect to the negative terminal.
Further, in the prior art, the positive terminal is usually exposed on the side and on the edge of the top of the battery pack. Thus, all tools in which the battery pack is to be used must be specifically designed either to make contact on the side or at just the top edge of the battery pack.
Also, in the prior art battery packs, the positive and negative terminals are generally located 180.degree. from each other in a diametrically opposed relationship with any terminal for a different voltage being located 90.degree. from either the positive or negative terminal.
Additionally, in the prior art, the battery casings are formed of unitary plastic construction thus making it difficult to modify, work on, or disassemble the battery pack for any reason.
The present invention overcomes the disadvantages of the prior art by providing a positive terminal that is exposed on one side of the battery pack and continuously across the top of the battery pack to the center thereof to allow for a variety of tool and charger configuration uses. In addition, the housing itself is designed to provide insulation of the positive terminal on the side of the battery pack from contacting the casing of the uppermost battery.
Further, the negative terminal is an elongated metal strip that extends from the base of the lowest battery to the uppermost portion of the battery pack. It is insulated from the battery casings by the housing itself. No insulating tape or sleeve is required to be placed over the battery cell casings. In addition, the positive and negative terminals are located 90.degree. apart at the top of the battery pack.
Further, an opening is provided in the upper side of the battery pack between the positive and negative terminals to expose the casing of the uppermost battery cell. This opening can be used to make electrical contact with the upper cell, thus providing a different voltage than that which is available at the positive terminal. Thus the tool can make contact directly with the side of the uppermost cell for a low speed tap. No separate part is required to create a terminal.
Also, a fuse link is located in a flat metal strip that either connects two of the batteries in series or in the negative terminal which extends from the base of the lowermost cell to the top of the battery pack. The fuse link, if on the side of the battery in the negative terminal, is exposed in a slot in the side of the battery pack where it can be readily ascertained if the fuse has opened.
Also, the battery pack casing is formed in two halves in a clamshell-type construction which snap together over the stacked batteries to form an integrated battery pack. A locking cap not only provides a mechanism which secures the two halves of the battery housing assembly together but also provides the mechanism that locks the battery housing assembly into the tool in which the battery pack is placed. The locking mechanism comprises a T-shaped projection on the locking cap on each side of the battery pack. The T-shaped portion requires no outwardly extending projections for locking the pack into the tool and thus can be inserted in a smaller space in the tool than the prior art battery packs.
A removable end cap is inserted in the locking cap which prevents the locking cap from being removed from the tool or shifted from its proper position for alignment purposes.
Thus it is an object of the present invention to provide a rechargeable battery pack that is formed by a housing having split sections that are detachably connected to each other, the housing sections having integrally formed therein passageways for the positive and negative terminals to provide insulation of the terminals from the battery cells.
It is also an object of the present invention to provide a battery pack in which the positive terminal is exposed continuously from the top center of the battery pack to and partially down one side thereof to allow for variety of tool and charger configuration use.
It is a further object of the present invention to provide a negative terminal in the form of an elongated metallic strip extending from the base of the lowermost cell alongside of the battery pack to the top with the negative terminal being positioned 90.degree. from the positive terminal and being accessed only from the sides.
It is still another object of the present invention to provide a fuse link in the negative terminal by reducing the cross-sectional area of the elongated ribbon-type connector in one location by an amount sufficient to destroy the reduced area in the event of a predetermined amount of current flowing in the ribbon connector forming the negative terminal.
It is a further object of the present invention to provide a low speed electrical tap with an opening formed in the uppermost portion of the side of the housing between the positive and negative terminals such that the casing of the uppermost battery can be directly contacted only from the side of the battery pack.
It is also an object of the present invention to provide a fuse link formed of a thin metallic ribbon connector having a reduced cross-section in one area with the fuse link located either between the middle and lower battery cell or in the negative electrode extending from the bottom of the lowermost cell to the top of the battery pack.
It is yet another object of the present invention to provide a locking cap which has resilient levers in the shape of a "T" that engage with corresponding depressions in the tool to lock the battery pack in the tool.
It is still another object of the present invention to provide an end cap which serves as a locking mechanism to aid in proper alignment of the housings and the lock cap as well as to secure the assembly together.